i totally agree.  the only way i get the kind of action that you are talking about is when i'm going against several unfair AIs with an emphasis on defence.  only then, after 3 hours mind you, do i get to fight large fleet battles.  when the AIs aggressive, i'm on the defensive for most of the game...

From what I've seen and read the AI is still being worked on (As in being programmed too work with the new ships and stuff) so its a bit derpy at times almost all the friggen time.

So give it time till later betas it seems

(edit) Bah ninja'd by ryat

After some mayor testing I found that the AI started acting a lot like it did in diplomacy starting with the level unfair. It plays a lot more agressive in 1on1, although it still hestitates a lot when trying to get to a heavily defended planet. Unfair is also the first AI I encountered to actually build frigates, anything below barely builds up all its caps (unfair actually filled all fleetpoints, wow did that bugger struggle against me. 70 Ogrovs hitting my starbase ftw).

Judging from the general behaviour I would figure the Rebellion beta unfair AI is around the level of the diplomacy hard AI in terms on how much a challenge it is to beat.